Predose infant nevirapine concentration with the two-dose intrapartum neonatal nevirapine regimen: association with timing of maternal intrapartum nevirapine dose.

Objective: To evaluate cord blood and predose nevirapine concentrations in infants exposed to the two-dose intrapartum neonatal nevirapine regimen.

Methods: The authors obtained plasma samples for nevirapine assay from cord blood and just prior to the 48-hours to 72-hours after birth neonatal nevirapine dose from a subset of infants participating in PACTG 316, a randomized, placebo-controlled trial of the two-dose intrapartum neonatal nevirapine regimen added to standard antiretroviral therapy.

Results: Nevirapine concentrations were measured in 109 cord blood samples and 149 predose samples. Cord blood nevirapine concentrations were below the target concentration of 100 ng/mL (10-times the in vitro IC(50) of nevirapine against wild-type HIV) in eight (7%) of 109 infants (95% confidence interval [CI], 3%-14%); the concentrations in six of these infants were below the assay limit of quantitation. Predose infant nevirapine concentrations were below 100 ng/mL in 23 (15%) of 149 infants (95% CI, 10%-22%); the concentrations in 13 of these infants were below the assay limit of quantitation. Lower predose nevirapine concentrations were associated with lower cord blood concentrations and a shorter interval between maternal dosing and delivery. All but one of the infants with predose nevirapine concentrations below the assay limit of quantitation were born less than 2 hours after maternal dosing.

Conclusion: Infants born less than 2 hours after maternal nevirapine dosing during labor should receive a dose of nevirapine immediately after birth in addition to the standard infant dose at 48 to 72 hours.